Muslims are organizing voter registration drives in response to proposals by Donald J. Trump and Ted Cruz for Muslim registries, immigration bans and police patrols of their neighborhoods.

• Top U.S. universities are subpoenaed.

A House committee empaneled to investigate Planned Parenthood has issued 17 subpoenas to universities demanding the names of researchers, lab technicians and administrative personnel associated with fetal tissue research. Some researchers see it as an effort to shut down scientific inquiry.

The panel was created after the release of secretly recorded videos purporting to show Planned Parenthood officials trying to profit illegally from the sale of fetal tissue. The videographers have since been indicted in Texas on charges of tampering with a government record, a felony.

• The N.F.L.’s dubious research.

Concussion research conducted for years by the N.F.L. was deeply flawed, an investigation by The Times shows. More than 100 diagnosed concussions were omitted from the studies.

We also uncovered how the league shared lobbyists, lawyers and consultants with the tobacco industry, which used questionable science to play down the dangers of smoking. We’ve rebutted the N.F.L.’s response to the article.

• More history-making visitors to Cuba.

Days after President Obama’s visit to Havana, the Rolling Stones are playing a free open-air concert there today.

It’s the band’s first performance in a Caribbean country, let alone Cuba, and about 400,000 people are expected to attend. Cuba once banned Western rock and pop music.

Business

• Automakers will unveil new models today at the annual New York International Auto Show. New-vehicle sales are on pace for another record year in the U.S.

• Judge Merrick B. Garland’s record as an appeals judge suggests that he might be the best Supreme Court nominee Republican senators could hope for where business issues are concerned, our columnist writes.

Noteworthy

• New reads.

Among this week’s fiction releases: “The Nest,” about a wealthy, dysfunctional family in New York; “Terrible Virtue,” a novel about Margaret Sanger, the founder of Planned Parenthood; and “The Association of Small Bombs,” which follows a terrorist attack and its fallout.

James Patterson, the world’s best-selling novelist, will start testing a line of short novels that cost less than $5 and can be read in a single sitting.

• Signs of springtime.

We turned to scientists and asked them to decode the seasonal changes around us, and to reveal some that we might not know to look for.

• Is your university a university?

Trump University’s difficulties remind us that there is a long history of giving the label “university” to organizations that don’t deserve it, or that only slightly resemble one.

Back Story

The Easter holiday is a time of music, in which one musical instrument plays a central part: the pipe organ.

Mozart once called it “the king of instruments.”

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Pipes at Our Lady Refuge Church in Brooklyn.CreditBryan Thomas for The New York Times

The first known organ was the Greek hydraulis, or water organ, from the third century B.C. But it didn’t evolve into the instrument we’re familiar with until the 17th century.

Musical instruments used to be considered too secular for church, but the pipe organ began to gain acceptance, some believe, for its power to lift the soul.

Today, the instrument’s rich and resonant sounds seem almost inseparable from the religious setting. A major portion of its repertoire — among the largest and oldest of all the instruments in Western music — is sacred in nature.